A SrGa2S4:Eu (hereinafter, written as SGS) phosphor is attracting attention as a green light emitting phosphor to be excited by a blue LED because the phosphor is excited by light in near-ultraviolet to blue regions. The SGS phosphor has a high color purity and high light emitting efficiency. Furthermore, by substituting Ca for the Sr site in the SGS phosphor, the wavelength of the phosphor may be increased approximately to 560 nm (refer to Patent Literature 1, for example).
Patent Literature 1 describes production of a green light emitting phosphor by preparing a powder containing europium and strontium from a solution containing a europium compound and a strontium compound, mixing the resulting powder and a powdered gallium compound, and performing firing, wherein the green-emitting phosphor is composed of (Sr,Ba,Ca)1-xGa2S4:Eux (where 0.10≤x≤0.20, preferably 0.10≤x≤0.18), and the value of (internal quantum efficiency/absorption efficiency) is 0.7 or more.
Patent Literature 2 describes an XRD pattern using a CuKα ray, of a phosphor including a host crystal containing Ca, Ga, and S.
However, the aforementioned conventional phosphors still do not have sufficient conversion efficiency as a green light emitting phosphor to be excited by a blue LED, and a green phosphor having higher conversion efficiency is required.